The invention relates to a method for connecting an electrical conductor with an electrical contact part, wherein the contact part has deformable legs and the legs are deformed by means of a bending die so that they force fittingly press the conductor together with the contact part. Further, the invention relates to a device with a bending die for connecting an electrical conductor with an electrical contact part, wherein the contact part has deformable legs and the bending die is configured to deform the legs so that they press the conductor force fittingly together with the contact part.
For electronic and electrical components of a motor vehicle for example the vehicle's electrical system, the connection of contact parts and lines usually occurs via a mechanical, force fitting connection, the so called crimp connection. In the crimp method at least two components are force fittingly interconnected by plastic deformation of at least one component. Usually, a contact part has so called legs or crimp flanks, which are forcibly pressed together with the strands of a cable by squeezing. This does normally not achieve a material connection. According to the sate of the art it is common to achieve a honey comp like pressing of the strands in the contact part by a pressing degree of about 20%. In addition, a support of the legs should be achieved to counteract a possible springing back.
The quality control of such crimp connections usually is usually performed by the so called crimp force monitoring, in which the force which has to be applied for the crimping or bending is measured in dependence on the bending path. The force integrated over the path results in the performed work, wherein in the crimp force monitoring the difference in work between a crimped contact part without line and a crimped contact part with line is used as a measure for the quality of the crimp connection. A difference in work of about 30% allows diagnosing missing strands of a cable, an insufficient pressing of contact part and line, and changed crimp parameters (for example crimp height).
The crimp methods known from the sate of the art have two significant disadvantages:
At very small line cross sections (smaller than 0.35 sq. mm) or great sheet thickness of the contact part in the deformed region, the measured work difference is so small that a sufficient monitoring of the crimp method is no longer possible. For example, missing strands of a cable can then no longer be identified. However, when individual strands of the cable are missing in the crimped region, the pressing degree in the crimp decreases and the electrical contact resistance between the conductor and the contact part can increase to become infinite. As a result, an electrical functionality of the connection is no longer given.
A typical material for the deformable contact part is metal. Because every metal has elastic properties, an insufficient support of the deformed crimp legs can result in an undesired springing back of these legs. This can lead to a deterioration of the contact between the deformed contact part and the conductor and the electrical resistance between the two components increases. The quality of the crimp connection is decreased.
From DE 103 58 153 A1 a connection method is known in which a cable is first crimped together with a contact element and then laser welded with the latter in three individual steps. The crimping and the laser welding are performed in two separate devices and thus also in separate work steps.
DE 10 2004 053 126 A1 discloses a device in which an electrical conductor is crimped together with a contact element and welded in the same work step. The crimp flaps of the contact element are pressed with a special crimp tool. The crimp contact is generated between the sheath of the electrical conductor and the crimp flaps of the contact element, whereas the welding is performed at a different site between a conductor end and the contact element. During welding, an electrical current flows via welding electrodes through the elements of the conductor to be connected and the contact element.
From DE 198 40 214 C2 a method is known for pressure welding by means of which lines between the flaps of a line-holding part is fixed. For this, the lines are first placed into the line-holding part and its one flap is pressed overlappingly under the other flap by using an anvil and a crimp die. Subsequently, the flaps are welded together.
DE 100 07 258 A1 discloses a mobile cable connector in which a wire bundle is inserted into a slanted cylindrical metal sleeve. At the slanted insertion opening, the wire bundle is then ultrasound-welded with a side of the sleeve via two electrodes.
DE 103 52 482 A1 describes a device with which the strands of different cables can be welded together. In addition, it enables crimping of the electrically insulated regions of the cables.
From DE 30 17 364 A1 a method is known in which the strands of a cable are first crimped with a flat plug in that a die stamp presses the metal legs of the flat plug together. The die stamp also serves for ultrasound-welding strands and flat plugs to one another.
Also from DE 10 2007 032 584 B4 a device is known for producing crimp and welding connections. Here, the crimp of a contact element is first closed about the insulation of a cable, and in a second step the insulated cable end welded together with the contact.